Method of and apparatus for production of metal powder by end milling of ingots



Feb. 14, 1950 w, PAUL Er AL 7 2,497,738

METHOD OF AND APPARATUS FOR PRODUCTION OF METAL POWDER BY END MILLING 0F mcows Filed Oct. 20, 1944 2 Sheets-Sheet 1 INVENTORS WPczuZ jEmestM.H01nmel m am? Feb. 14, 1950 w. w. PAUL ET A 2,497,738

mm'aon OF AND APPARATUS FOR PRO non 0F METAL POWDER BY END mums OF mco'rs y A Filed Oct. 20, 1944 r I 2 Sheets-Sheet 2 ENTORS William $1 6111] .ErncstMfimmcZ 21. .227 24, MHM/ Patented Feb. 14, 1950 METHOD OF AND APPARATUS FOR PRODUC- TION F METAL POWDER. BY END MILL- ING OF INGOTS William w. Paul, Carnegie, and Ernest M. Hommel, Pittsburgh, Pa., assignors to The 0. Hommel Company, Pittsburgh, Pa., a corporation of Pennsylvania Application October 20, 1944, Serial No. 559,638

16 Claims.

The present invention provides certain improvements in the production of metallic powders, particularly powders of soft metals such as lead, aluminum, magnesium and the like. I

Such metal powders find extensive use, and because of the inflammable nature of certain of such powders, they cannot safely be prepared by many of the operations which are applicable to the fine division of metals. less subject to oxidation. Magnesium is a particularly inflammable metal, and the present invention will be described with particular reference to the production of magnesium powder, although it is equally adaptable to the production of powdered lead, aluminum, zinc, copper, or other soft metals.

Under the present war conditions, magnesium powder is of high importance as a component of incendiary bombs, although it has many other industrial uses, as in photography and in the production of structural light metal alloys.

In view of the softness of metallic magnesium and because of its ease of ignition, the usual manner of preparing it is to reduce an ingot of the metal by attrition against a cutting or grinding tool of suitable characteristics.

For this purpose, there is provided a face plate having a plurality of ingot-receiving receptacles or pockets into which the ingots are placed, the ingots being held in the pockets by a frictional force fit. The face plate is rotatable about an axis, so that each ingot is carried around the center of rotation and into engagement with a rapidly rotating cutting tool which cuts or grinds the end of each ingot into finely divided particles. As the ingots become shorter, the cutting tool progressively moves towards the face plate and pockets therein.

It is apparent that machines of this character operate at high speed, and that the ingots must be firmly held in the holder-pockets, as the dislodgment of an ingot from its holder might seriously interfere with or Jam the operation of the machine, and even result in a spark being produced, or heat generated to asuflicient extent to ignite the metal particles.

The machines employed for this purpose, prior to the present invention, have the disadvantage that the mechanical construction of the ingot holders is such that substantial lengths of the ingots contained in the holders cannot be reached by the cutting tool, so that substantial amounts of the metal ingots must be remelted in order to recover the same. Such remelting involves additional cost, and, unavoidably, loss of some of the metal through volatilization.

The present invention provides mechanism and method of utilizing the same, which enables the reduction of the ingots to be progressed substantially further than has been possible heretofore, leaving much shorter stumps of metal ingots which cannot be reached by the cutting tool.

As commercially cast, magnesium ingots are round in cross section and have a slight taper toward one end. Generally speaking, the present invention provides a construction of holders for receiving and frictionally rigidly holding the ingots.

These holders can be arranged in clusters, such clusters of holders being removably carried as a composite unitary cluster on a face plate, each of the holders being in the form of a ferrule or sleeve-like holder, and have a diameter greater than the smallest diameter of the ingot, but Just about equal to or slightly less than the largest diameter of the ingot.

In order to receive the ingots the holders are dismounted from the face plate, the ingots are dropped through them as far as they will go, and then subjected to hydraulic or mechanical pressure to force the ends of larger diameter down into the holders. The ingots thus are forced under heavy pressure into the holders, and because of the relative softness of the metal, it becomes pressed into the holders in such manner as to remain completely rigid. The holders with the ingots secured therein in this manner are mounted on the face plate of the machine in which the ingots are to be reduced. As the face plate is rotated, the ingots are engaged in the usual manner by a transversely arranged multiple tooth cutter, which progressively cuts away the ends of the ingots and which moves toward the face plate as the reduction of the ingots proceeds.

when the cutter has approached as closely as it may safely be brought to the holders, the machine is stopped, the clusters of holders removed, and the short ends of the ingots which then remain in the holders are again subjected preferably by hydraulic pressure and partly ejected thereby from the holders, only a very short length of the ingots then being engaged by the holders. The clusters of holders then are remounted on the face plate and the small lengths are thereupon further reduced. It will be understood that while one cluster of holders is removed, either for rechanging or resetting of the short ends of the ingots, other clusters of holders may be mounted on the machine, thereby reducing the idle time of the machine and avoids the machine standing idle while the holders are being prepared.

The method of securing the ingots in the holders by pressure eliminates any need for adjustable clamping elements on the holders and assures the ingots being rigidly and immovably held. When the ingots have been reduced to short lengths, less holding power is required, and, consequently the short ends of the ingots may safely be pushed partway out of the holders with the assurance of there still being suilicient friction to retain the short ends immovably in the holders.

The invention will be understood more clearly by reference to the accompanying drawings,

wherein Figure 1 is a front elevation of a fragment of a face plate of a lathe or similar machine, having clusters of the improved ingot-holders of the present invention mounted thereon, the view showing substantially the upper half of the face plate, one of the illustrated clusters of holders having ingots received therein;

Figure 2 is a fragmentary sectional elevation of a lathe having a face plate mounted thereon provided with the improved holders of the present invention, with ingots in the holders and a cutting tool adapted to reduce the ingots to powder, the view through the face plate and holders being taken on the line 11-11 of Figure 1, looking in the direction of the arrows;

Figure 3 is a view partly in section, showing the first step of securing an ingot in an improved holder of the present invention;

Figure 4 is a view similar to Figure 3, showing the ingot forcibly pressed into the holder;

Figure 5 is a view, partly in section, showing the relative position of an individual holder and ingot, and the relative length of ingot and holder after the first machine powdering operation has been performed;

Figure 6 is a view similar to Figure 5, but showing the relative position of the holder and ingot after the second pressing step, wherein a still substantial portion of the residual ingot remaining after the first machine powdering operation has been forced from the holder, but yet a sufficient length of the end of the ingot is frictionally retained in a press-fit in the holder for forming a rigid support during a subsequent machine powdering operation;

Figure '7 is an enlarged perspective view of Figure 6; and

Figure 8 is a diagrammatic view showin a still further modified embodiment of an apparatus and procedure for practicing the present invention.

Referring more particularly to the drawings, and first to Figures 1 and 2, there is shown a fragmentary portion of a face plate It of a lathe or like machine, having a plurality of the improved holders of the present invention, indicated at 2, mounted thereon. The holders 2 are assembled in clusters and suitably secured together, as by welding, soldering, brazing, or the like. The holders 2 are so assembled that the resulting clusters, as indicated at 8, are of a general quadrant sector form.

The individual holders 2 preferably are cylindrical or sleeve-like in shape for receiving metal ingots indicated generally at 4, which are cast with a taper as clearly shown in Figure 2. The diameter of each holder 2 is larger than the smallest diameter of the ingots 4, but less than the largest diameter of the ingots, so that the ingots may be pressed rigidly into the holders, and held by the resulting press fit against displacement by a powdering tool operating on the ingots. The manner of inserting the ingots in the holders will be described in detail hereinafter.

When the individual sleeve-like holders containing the ingots are assembled in the relation above referred to, so as to form a composite unit or cluster 8, a unit is formed which may be handled readily and conveniently, for mounting upon the face plate l8 of a lathe or similar machine, and for completing the insertion of the ingots as referred to above and as will be described in detail hereinafter.

The composite cluster or unit of holders, indicated at 8, may be mounted firmly on the face plate l6, by means of bolts or studs l1, l8, passing through an aperture of the short sleeves or ferrules H], H, which are integrally fixed to the cluster at the outer perimeter thereof.

Various means may be utilized for firmly securing the central portion of the cluster, or a plurality of clusters, to the face plate. A preferred mounting is shown in Figures 1 and 2. As shown in these views, a flange-like pin 48 may be secured integrally to a holder 36 of the cluster nearest the center or axis 39 of the face plate 18, such holder 35' corresponding to the one having its axis 48 on the smallest of the concentric circle 36. Each of the face clusters of the ingot holders disposed on the face plate l6 would present such a pin 48 at four different points apart, and symmetrically disposed about the axis 39. The pin or projecting flange portion 48 preferably would extend throughout the length of the holder.

A threaded stud or bolt l4 may be disposed and held rigid in any suitable manner as the axis 38 of the face plate adjacent to the pin flange-like members 48 so that a washer-like member l3 may be carried by the threaded end of the bolt I4 so as to overlap and lie in contact with one end of each of the four flange-like projections 48 on each of the respective clusters. A nut l5 may be threaded on the stud [4 so as to hold the flange portions 48 firmly between the face plate I6 of the lathe and the washer l3 and nut 15.

It will be understood, of course, that various other specific means may be employed to perform such holding function which will occur readily to those familiar with the art.

It will be noted that while the centers or axes 48 to 44, 43' and 44', inclusive, of the various ingot holders, do not lie in any radial line extending from the axis of the face plate 39, nevertheless the axis of the various holders are so disposed that they do lie on the various concentric circles 36, 31, and 38. The axes 4|, 42 of the respective holders on the are 31, are offset within the quadrant cluster from a line joining the axes 48, 43 and axes 48, 44, respectively.

The cutter 28, preferably a rotating toothedcylindrical milling-like cutter mounted on a shaft 38, may be driven in any suitable and conventional manner. The cutter 28, extends transversely of the lathe in cutting relation to the ends I of the ingots for a distance corresponding to the radius or one-half the diameter of the face plate of the lathe. By such an arrangement it Suitable conventional means such as a feed' screw 25 of the lathe, may be provided forfeeding the cylindrical cutter 28 longitudinally of the various ingots carried by the clusters of holders so that the machining operation on the ends I of the ingots progresses from the outer end of each ingot 4 inwardly toward the lathe face plate It on which the cluster of holders is mounted. The feed screw 25 of the lathe feeds the tool carriage or carrier 26 along the slides or track supports on the lathe body or bed 20.

A conventional fragmentary showing of the lathe parts is shown in Figure 2, wherein a shaft 2| is shown as being suitably supported in a hearing 22, which shaft may be driven in a conventional manner either through gearing or pulleys. The face plate I 6 may be mounted on the end of the main shaft 2| in any suitable and conventional manner, such as' for example; by a pin connection 24 extending through a hub portion 25 on the back face of the face plate [6.

There may now be described in greater particularity, how the ingots 4 are held in the respective holders 2. For this purpose reference may be had to Figures 3 and 4, which views indicate diagrammatically the first of a series of forcible or press fitting operations, wherein a holder 2 is forced upon one end of an ingot'so as to have a firm frictional gripping engagement therewith, so that when the sleeve-like holder 2 is brought into assembled relation with other holders with ingots therein, and mounted on face plate it, as shown in Figure 1, the force fit of the ingots in the various holders comprising the cluster formation constitutes the sole means of firmly holding the ingots in proper position within their respective holders without the necessity of employing independent and separately adjustable and movable clamping means such as heretofore employed in the art. With reference to such clamping means, it may be noted that it would be diilicult, if not impossible, to assemble the holders in such a closely assembled and clustered relation as shown in Figure 1, if separate and independently movable clamping means were employed for each of the separate holders, because such separate and independent movable clamping means would take up a certain amount of space which would preclude such a closely assembled position for the holders with the ingots therein, as shown in Figure 1.

Preferably, the ingots 4 are cast with a slight taper, as has been pointed out above, this taper being illustrated as extending from a larger end 5 to a smaller end 6, which is the portion of the ingots which presents the end face 1 of the ingots to the cutter 28 during the powdering operation.

When magnesium is the metal being powdered, ,0;

it has been found in practice that an ingot of the metallic magnesium having a length of about sixteen inches and having a taper of about oneeighth of an inch difference in diameter per sixteen inches of length is satisfactory in forming a firm and rigid fit with the holders.

In a typical magnesium ingot employed in the practicing of the present invention, the larger end measures about four and one-sixteenth inches in diameter,

diameter of about three and seven-eighths inches at the smaller end I.

For such an ingot the length of the sleevelike holder 2 may be about three inches, or somewhat less than one-fifth of the total length of the ingot.

Further reference to these relations will bemade hereinafter.

Now, referring particularly to Figure 3, the advantage of a tapering ingot will become apparent.

As shown in Figure 3, the sleeve-like holder 2, dismounted from the face plate It, maybe held in any suitable position to receive the smaller end of the ingot 4. The ingot initially is pressed within the holder 2 until a position is reached in which the end 3 0f the holder is engaged with the larger end of the ingot 4 by slight frictional engagement so that a portion 5 of the larger end (see Fig. 3) extends beyond the end 2 of the holder.

The inner end of the holders 2 preferably is formed with a series of kerfs 20, these kerfs forming a series of finger-like prongs, which may be sprung inwardly to serve as guides for centering the ingot 4 when the ingot is inserted initially in the holder 2.

The holder 2 and the ingot 4 therein then are subjected to hydraulic or mechanical pressure transmitted to the projecting end 5 through a plunger 3|, the holder 2being held in any suitable manner against movement. Pressure of the plunger 3! against the end 5 of the ingot is sufficient, and is continued sufficiently long, to force the ingot through the holder until the large end 5 of the ingot .is substantially flush with the end of the holder 2, so that the holder 2 has a frictional forced fit with the ingot throughout the entire length of the holder 2, so that the parts assume the relative position indicated in Figure 4.

After each of the individual holders has thus received an ingot, the holders are assembled in clustered relation as shown in Figure 1, and mounted on the face plate It as has been described above. arrangement may be employed so that the cluster of holders as a composite unit may be supported in such a manner that the smaller end B of the ingots may be inserted within each of th respective holders, so .that it is not necessary to deal with the separate holders in forcing the ingot bars therein, although obviously, the individual and separate ingots may be forced into described above, the end surfaces 1 of the ingots are presented to milling cutter 28.

, During the first portion of the machine powdering operation, the length of the ingot which is inaccessible to the cutting tool is indicated generally by the reference number 32 in Figure 5. Such entire portion of the ingot which is inaccessible to the tool, would have, in accordance with the practices heretofore employed, only: a scrap value, and the entire lengths of the stubs would have to be remelted to recover the metal for subsequent use.

As indicated in Figure 5, the length of the ingot which becomes scrap in accordance with the prior practices, included a length equal to the length of the holder 2 plus an additional short the ingot being tapered to all length 50 which extended from the end of the It is apparent that a suitable 7 holder, owing to the practical impossibility of machining the ingot up to a point which is flush with the outer end of the holder 2.

In order to lessen the length of the scrap stub of the ingot whichheretofore has been inacces sible to the cutting tool 28, the present invention contemplates .a second step which comprises application of the plunger ii to the ingot stub under sumcient pressure to force the ingot stub further out of the holder, as indicated in Figure 6, the further length of the ingot which is thus rendered accessible to the cutting tool 2., being represented by the reference numeral 84 on Figures and 6.

As has been indicated above,'the length of the sleeve-like holder 2, which is forcibly pressed for its full length upon one end of the ingot 4 in the first instance amounts, in practical operation. to about one fifth of the full length of the ingot as mounted on the face plate for the first powdering operation. According to the practices as carried out prior to the present invention about one fifth, or twenty per cent, of the original length of the ingot was scrap, and considered to have only scrap value.

However, after the second pressing operation has been carried out in accordance with the present invention, a substantial length of the heretofore inaccessible ingot stub is forced outwardly from the holder 2 by the plunger 3|, to which a sufllcient force is applied, as by a hydraulic or mechanical press, or in other suitable manner, until only a relatively very short length of the ingot such as that indicated by the reference character ii in Figure 6 remains inaccessible to the cutting tool and becomes scrap, and an additional length of ingot extending from the end ll of the ingot stub to the line 1 (Fig. 6) is rendered accessible for powdering. The length of the ingot stub which remains inaccessible t9 the cutting tool after the second powdering operation which follows the said second pressing is only that represented by 5| on Figure 6. The length of this residual stub Si is only sumcient to support the powdering cutting upon the further pressed out length 34.

It is noted that this residual stub which remains after the series of steps of the present invention is substantially less than the scrap length 32 (Figure 5) which is left when the prior art methods and practices are followed. This savings may represent a length equal to one-half or more of the length of the holder 2. When it is considered that in the form shown in the drawings, the machining operation is performed at one setting or mounting of the four clusters upon the face plate of the lathe representing twentyeight of the ingots, the accumulated or total saving in scrap results in a substantial amount. A further advantage in having the holders disposed integrally in a close clustered relation is that during the second powdering operation, when a substantial length of the first ingot stubhas been forced out from the holder, the adjacent holders of any particular holder of a cluster serve to support or retain such particular holder in proper position. Expressed in another way, the cutting force effective upon the end of any given ingot is transmitted to the particular holder for that particular ingot, and also to the other holders of the cluster that are integrally related by being in contact with each other. Such an arrangement. provides an additional advantage over a structure in which the holders are separated or spaced from each other and having a 8 1 support for each of the'respective holderssobiy from one end of the holders.

One of the advantages of performing the powdering attrition on a plurality of the assembled 5 ingots where such ingots are composed of a readily combustible metal, such as ma nesium. and where the ingots are of small size, rather than machining a single ingot having the same mass or weight as a number of separate smaller ingots, is that in the arrangement of the present invention, the machining operation is carried out in a safe and satisfactory manner in which excessive temperatures are minimized or avoided, so that danger of spontaneous ignition of the magnesium is avoided. A large number of smaller ingots presents a larger surface for actual cooling than would the same mass of metal if contained in a single piece, or a less number of pieces. An integral, continuous larger mass of solid metal would tend to conduct the heat generated from the frictionof the cutting tool to other portions of the solid mass, which would lack the requisite surface effective for radiation of the generated heat, as does the same mass arranged as a plurality of smaller pieces.

While the foregoing description sets forth in detail certain preferred embodiments of the invention, an apparatus and procedure as set forth in Figure 8 may be employed. In this view a single ingot 4a may be presented to a cutter 20a similar to cutter 2!, described above. Instead-of clusters of holders 2 mounted on a plate, as described in Figures 1 and 2 for presentation to the cutter, the teeth to of holder 2b are mounted so as to enable a ram 5|, which may be either mechanically or hydraulically operated, to enter the open end 52 thereof, through which end the ingot 4a is inserted, for continuously forcing the ingot outwardly against the cutter 28a during the powdering operation, substantially the entire length of the ingot being thus accessible to the cutting tool. The tubular portion to of the ingot holder serves as a guide for centering the ingot into the serrated end 20. In order to permit insertion of an ingot into the holder 31), the ram 50 may be retracted, as indicated by dotted lines, to permit access to the open end 52 of the holder.

The apparatus and method of Figure 8 is of advantage where only a small yield of powder may be desired, the arrangement permitting the powdering of single ingots, but the powdering is a continuous operation, not requiring demounting of the ingot holders for a second pressing operation, the ram 50 being adapted to feed the ingot continuously against the cutter until powdering thereof is completed.

We claim as our invention:

- 1. Apparatus for producing metal powders, which comprises the combination with a face plate, of mounting means for the face plate, a plurality of sleeve-like receptacles for receiving ingots of metal to be powdered, means integrally uniting the said receptacles .to one another, thereby forming an integral cluster of the said receptacles, means for removably uniting the cluster to the face plate, metal comminuting means disposed to operate on metal ingots received in the said receptacles, and mechanism for presenting each ingot to the conmiinuting means 10 for reducing each ingot to powder.

2. Apparatus for producing metal powders, which comprises the combination with a face plate adapted to be rotated about an axis, of a plurality of sleeve-like holders for receiving and holding metal ingots to be powdered. means integrally uniting the holders together to form a cluster thereof, the holders of the cluster being symmetrically disposed in the cluster, and means for removably mounting the cluster on the face plate with the holders of the cluster having their longitudinal axes disposed on radii of circles of increasing length from the axis of rotation of the face plate, the said circles being concentric with the axis of rotation, whereby metal ingots received in the holders may be brought into successive engagement with a metal comminuting tool responsively to rotation of the face plate about its axis of rotation.

3. Apparatus for producing metal powders, which comprises in combination, a plurality of ingot holders adapted to receive and hold ingots of the metal to be powdered, means integrally interconnecting the said ingot holders into a unit cluster thereof, a face plate adapted to be rotated about an axis, and means for attaching the unit cluster of ingot holders to the face plate with the holders having their longitudinal axes normal to the face plate, the said ingot holders being adapted to hold firmly by frictional contact ingots placed in the said holders, the said ingots having their outer ends in a common Plane normal to the axis of rotation of the face plate, the said ingot holders being adapted to receive and to hold the ingots with a press force fit, the ingots being held rigidly in the holders by the said force fit independent of any other clamping means between the holders and ingots retained therein, the holes being of uniform diameter throughout substantially their whole length and having integral resilient fingers formed along their peripheries at the ends thereof outermost from the face plate which spring radially inwardly beyond the normal diameter of the holder when there is no ingot in the holder.

4. Apparatus for producing metalpowders from i a plurality of tapered ingots of metal, which comprises in combination, sleeve-like holdermeans adapted to receive the ingots, the holder means having a diameter greater than the smallest diameter of the ingots, but somewhat smaller than the largest diameter of the ingots, whereby the ingots may be rigidly retained in the sleevelike holder means by a press force fit obviating any other independent clamping means between the ingots and the holder means, means uniting the holders integrally together in a unitary cluster, a face plate mounted for rotation about an axis, and means for demountably securing the unitary cluster of holding means to the face plate, with the holders and ingots retained therein having their longitudinal axes perpendicular to the face plate and having such dimensions that the outer ends of the ingots lie in a common plane normal to the axis of rotation of the face plate.

5. In mechanism for mounting work-pieces for machining operation thereon, the improvements which include a plurality of sleeve-like holders for the work-pieces adapted to rigidly. hold the work-pieces solely through a friction press fit between the work-pieces and the holders'throughout substantially the entire lengths of the holders, means for integrally uniting the holders in resulting cluster on a supporting face plate, the holders being radially disposed in the said cluster, the cluster being removable as a unit from the face plate for charging the holders thereof with work pieces.

6. In mechanism for mounting work-pieces for achining operations thereon, the improvements a cluster, and means for removably mounting the held in the holders solely by a frictional press fit between the holders and the work-pieces throughout substantially the entire lengths of the holders, and means for mounting the integral cluster of holders on the face plate with the holders in the cluster radially disposed relative to the axis of rotation of the face plate, whereby, responsively to rotation of theface plate, each work-piece mounted in the holders rotates in a circular path outside of the axis of rotation of the face plate.

7. In mechanism for mounting work-pieces for machining operations thereon, the improvements which include, in combination, a face plate, means for rotating the face plate about an axis, a plurality of holders integrally united into a segment-shaped cluster, the said holders being adapted to define enclosing sleeves for receiving the work-pieces, the holders having diameters proportioned to the diameter of the work-pieces whereby the work-pieces are firmly and rigidly.

held in the holders solely by a. frictional press fit between the work-pieces and the holders throughout substantially the entire lengths of the holders, and means for mounting the integral cluster of holders on the face plate with the holders radially disposed relative to the axis of rotation of the face plate, the said cluster of holders, when mounted on the face plate occupying only a fractional portion of the face plate, a plurality of the integral clusters being arranged in complementary manner on the face plate to substantially cover the same.

8. In mechanism for mounting work-pieces for machining operations thereon, the improvements which comprise a plurality of holders adapted to rigidly hold the work-pieces in a frictional press flt engagement therein, means integrally securing the holders together, thereby forming an integral cluster of the holders, a face plate adapted to receive a plurality of the said integral clusters of the holders-when disposed on the face plate in functioning relation therewith, means for securing a plurality of the clusters on the face plate, each cluster being secured to the face plate independently of the remaining clusters, the holders of each cluster being disposed in the said clusters to form, when the clusters are assembled on the face plate, a composite circular assembly of the clusters wherein the holders are disposed in concentric circles, each of which concentric circles forms a base line for the central axis of the individual holders. the first concentric circle from the center thereof having at least one individual holder for each quadrant sector of the face plate, and each succeeding adjacent larger concentric circle having twice the number of individual holders as the next smaller adjacent concentric circle.

9. In mechanism for mounting work-pieces for machining operations thereon, the improvements which comprise a plurality of holders adapted to rigidly hold the work-pieces in a frictional'press fit engagement therein, means integrally securing the holders together, thereby forming an integral cluster of the holders, a face plate adapted to receive a plurality of the said integral clusters of the holders when disposed on the face plate in functioning relation therewith, means for securing a plurality of the clusters side by side on the face plate, each cluster being secured to the face plate independently of the remaining clusters, the holders of each cluster being disposed in the said clusters to form, when the clusters are assembled and mounted on the face plate, a composite circular assembly of the clusters, wherein the clusters are disposed in concentric circles, each of which concentric circles forms a base line for the central axis of the individual holders, the

first concentric circle from the center thereof having at least one individual holder for each quadrant sector of the face plate, and each succeeding adjacent larger concentric circle having twice the number of individual holders as the next smaller adjacent concentric circle, the number of individual holders in any one of the series of concentric circles of increasing size, increasing in number and size in relation to the diameter of the work-pieces and extending outwardly from the center in a geometric progression, the number of individual holders on any one circle of the concentric series being equal to one-half of the number of the individual holders on the next larger concentric circles and twice the number of individual holders in the next smaller of the concentric circles.

10. In mechanism for mounting work-pieces for machining operations thereon, the improvements which include a plurality of holders adapted to rigidly hold the work-pieces in a frictional press fit engagement therein, means integrally securing the holders together, thereby forming an integral cluster of the holders, a face plate adapted to receive a plurality of the said integral clusters of the holders when disposed on the face plate independently of the remaining clusters, the holders of each cluster being disposed in the said cluster to form, when the clusters are assembled and mounted on the face plate, a composite circular assembly of the clusters, wherein the holders are disposed in concentric circles, each of which concentric circles forms a base line for the central axis of the in-' dividual holders, the first concentric circle from the center thereof having at least one individual holder for each quadrant sector of the face plate. and each succeeding adjacent larger concentric circle having twice the number of individual holders as the next smaller adjacent concentric circle, the means for securing the clusters on the face plate comprising a three-point support for each of the said clusters on the face plate, one of the said three-point support being disposed as a centrally positioned reactor point for machining forces applied to the work pieces, and two of the three-point support for each cluster of holders securing the cluster to the face plate at points intermediate terminal holders disposed on the outermost of the said concentric circles.

11. A method of comminuting metal ingots for making metal powder therefrom, which comprises frictionally securing the ingots in sleevelike holders, establishing a press-f1t engagement between the holders and the ingots, with the major portions of the ingots remaining free from the holders, powdering the ingots from the free ends thereof towards the holders until a first length of the ingots becomes inaccessible to a comminuting tool, and thereafter further expressing a second further substantial length of ingots from the holders, thereby enabling additional substantial amounts of the ingots to be brought into engagement with the comminutlng tool, while continuously maintaining the rigid press fit between the tool and residual lengths of the ingots, thereby minimizing the amounts of metal remaining permanently inaccessible to the comminuting tool without requiring remeltlng and recasting the said remaining metal.

12. A method of producing metal powders, which comprises supporting a portion of length of an ingot to be reduced to powder-like particles in a holder adapted to receive the ingot, effecting a firm frictional press fit between a portion of the ingot and holder, with an end of the ingot free from the holder, as well as a substantial length of the ingot, subjecting the free length of the ingot to an over-all attrition operation from the free end of the ingot towards the holder and simultaneously subjecting the ingot and holder to a continuous pressing operation during the time of the over-all attrition of the ingot to relocate it relatively to the holder, thereby continuously exposing successive incremental lengths of the ingot to the attrition operation while continuously maintaining the press fit between the holder and length of the ingot retained therein.

13. A method of producing metal powders, which comprises supporting a portion of length of an ingot to be reduced to powder-like particles in a holder adapted to receive the ingot, effecting a frictional press fit between a portion of the ingot and holder, with an end free from the holder, subjecting the free length of the ingot to an overall attrition operation from the free end of the ingot towards the holder, and subjecting the ingot in the holder to a continuous pressing operation during the over-all attrition of the ingot, thereby continuously exposing additional length of ingot to the attrition operation while continuously maintaining the press fit between the holder and ingot retained in the holder while continuously reducing the ingot to powder at the continuous free end thereof.

14. A method of producing metal powders. which comprises supporting a portion of length of an ingot to be reduced to powder-like particles, in a holder adapted to receive the ingot, effecting a frictional press fit between a peripheral portion of the ingot and holder, with an end free from the holder, subjecting the free length of the ingot to an o er-all attrition operation from the free end of the ingot towards the holder, and subjecting the ingot in the holder t a further pressing operation during the over-all attrition of the ingot, thereby exposing additional length of ingot to the attrition operation while continuously maintaining the press fit between the holder and ingot during the attrition of the ingot, the pressing operation being carried out with the ingot and holder in situ adjacent a cutting tool performing the attrition operation.

15. Apparatus for reducing metal in ingot form to finely divided particles comprising a rotatably mounted face plate, means on the face plate constituting sockets for receiving and rigidly holding ingots of metal therein with the ingots projecting from the face plate in a direction normal to its plane of rotation, a rotatable cutter extending transversely of the face plate with its axis of rotation transverse to the axes of the ingots in the holder, and means for effecting relative movement of the cutter and the face plate in the direction of the length of the ingots.

16. Apparatus for reducing metal in ingot form to finely divided particles comprising a rotatably mounted face plate, means on the face plate con- 13 14 stituting sockets t1for receiving and rigidly holding UNITED ST TE PATENTS ingots of metal erein wi h the ingots projecting from the face plate in a. direction normal to its fig i J i plane of rotation, a rotatable cutter extending 490'054 1893 transversely of the face plate with its axis of 5 684'043 g er 1901 rotation transverse to the axes of the ingots in 8928o8 C J i 1908 the holder, and means for efiecting relative 1 087024 g z 1914 movement of the cutter and the face plate in the 1188667 L 8 Jun; 1916 direction of the length of the ingots, each holder 1213896 3 Jan 1917 comprising a substantially cylindrical cup with 10 1250'645 er 8 De 1917 its outer end slit longitudinally and biased to 2121'089 gg 1938 spring inwardly Wnnm w PAUL 2,328,712 Domke Sept, '7, 1943 ERNEST M 2,368,870 Pagendarm Feb. 6, 1945 2,446,345 Snow Aug. 3, 1948 REFERENCES CITED The following references are of record in the file of this Patent: 

